April 21st was a slow day for ruby-throated hummingbird reports in Northern states. This map shows wind speed and direction on that day in the area just west of the Great Lakes. Think: Describe what the winds were doing on April 21. Why do you think we received so few new reports that day? What do you think a wind map might have looked like on April 18th: the day we received so many new reports?

Winds: April 21, 2009 (Note: The wider the arrow, the faster the wind speed.) Image: Windmapper.com